Add extractor for [videos.esri.com](https://videos.esri.com), a collection of videos relating to GIS.
Updated line numbers in the fragment portion of README links.
Closes #2147.
Fixes #6546. Not adding a test case as test_NBC has the same problem.
[rtvnhnl] Added new extractor
[funnyordie] Handle protocol-relative URLs (fixes #6490)
[iqiyi] update md5 salt (2015-08-10)
[youtube] Use the first v= argument in the URL
This is according to how youtube handles multiple v= values in one URL. Before this, it was possible to make a single URL show up differently on youtube itself, and if you downloaded/viewed it with youtube-dl/mpv